A variety of flavorants have been developed and proposed for incorporation into tobacco products. Illustrative of such tobacco flavorants are those described in U.S. Pat. Nos. 3,580,259; 3,625,224; 3,722,516; 3,750,674; 3,879,425; 3,881,025; 3,884,247; 3,890,981; 3,903,900; 3,914,451; 3,915,175; 3,920,027; 3,924,644; 3,937,228; 3,943,943; 3,586,387; and the like. The tobacco flavorants include compounds such as succinic anhydride; dihydroxyacetone; substituted pyridines; cinnamic derivatives; isovaleric acid; 6-methylhepta-3,5-dien-2-one; 2-butyl-2-butenal; 1,3-cyclohexadiene; alpha-pyrones; substituted butyrolacetones; pyrazines and thiazolidines; and the like.
Cooling compounds, particularly menthol, have been used extensively in tobacco products. Unfortunately, menthol has a high degree of volatility and also suffers from the disadvantage that it exhibits a relatively strong minty odor. Nevertheless, in spite of its disadvantages menthol is still extensively employed as a tobacco flavorant for the reason it has a physiological cooling effect on the mucous membranes of the mouth. Menthol flavorant in cigarette tobacco produces a cool sensation in the mouth during the smoking of a cigarette.
Other organic compounds are known which exhibit to some degree the properties of a physiological coolant. For example, N,N-dimethyl-2-ethylbutanamide is reported in French Pat. No. 1,572,332 as having a minty odor and a refreshing effect on mucous membranes. Other compounds of similar interest are 2,4,6-trimethylheptan-4-ol and 2,4,6-trimethylhept-2-en-4-ol as reported in Parfums-Cosmetiques-Savons, pages 17-20, May 1956.
More recently another group of organic compounds have been developed which are odorless and non-volatile, and which can function as physiologically active coolants. These compounds are the subject matter of U.S. Pat. Nos. 4,178,459 and 4,193,936, and are generically classified as N-substituted para-menthane carboxamides. Illustrative of a particularly interesting species as a prospective smoking tobacco flavorant is N-t-butyl-p-menthane-3-carboxamide: ##STR1##
The said patents describe a sequence of conventional reactions for producing the N-substituted para-menthane carboxamides. Thus, N-t-butyl-p-menthane-3-carboxamide is produced by the following sequence of reactions: ##STR2##
The reaction sequence is long and tedious, and the overall conversion from 3-p-menthyl halide to N-t-butyl-p-menthane-3-carboxamide is less than about 20 percent.
Accordingly, it is a main object of this invention to provide a novel process for producing N-(hydrocarbyl)substituted-p-menthane-3-carboxamide compounds.
It is a further object of this invention to provide a novel and efficient two-step reaction sequence for converting 3-p-menthyl halide to N-t-butyl-p-menthane-3-carboxamide.
Other objects and advantages of the present invention will become apparent from the accompanying description and examples.